Officers in ‘Operation Trammel’ now monitor suspects to see if their lifestyles reflect the amount of cash they are believed to have stolen or if they are passing it on.

A Metropolitan Police spokesman said: “Operation Trammel is a pro-active nationwide police operation to detect, disrupt and deter individuals who provide financial support to international terrorists by committing cheque and credit card fraud.” The Tamil Tigers—responsible for attacks in Sri Lanka—were believed to have organised a credit card sting involving up to 200 UK petrol stations in 2007.

And cops are probing a fraud which saw devices placed in chip and pin readers in 40 UK supermarkets. The devices transmitted card details by wireless technology to Pakistan.

Mr Lyons, of Business Risk Innovations, said: “These are well-organised criminal enterprises. Some of these groups have entire families with 10 or 20 people working for them.”

Tory MP Patrick Mercer, who advised Gordon Brown on fighting terrorism, said: “Our enemies are using these methods more and more frequently.”